WASHINGTON — In an immigration debate rife with calls to wall off Mexico, New England’s senators seem grounded in an alternate universe. Several want assurances that sweeping new legislation won’t fence off the region’s northern boundary, or otherwise disturb “free and open borders” with Canada.

Despite that difference, the region’s senators are in prominent roles to shape the legislation, which beefs up border security while also providing a path for illegal immigrants to become citizens.

Senator Patrick Leahy, a Vermont Democrat, will manage the floor debate, which could begin next week. Already, as chairman of the Judiciary Committee that reviewed and approved the bill last week, he engineered the amendment to maintain an open, fence-free border with Canada.

Republican senators Kelly Ayotte of New Hampshire and Susan Collins of Maine are seen as potentially important swing votes. They have yet to declare their positions, and are being targeted by activists on both sides of the issue.

Senator Bernie Sanders, a Vermont independent who caucuses with Democrats, has been leading the critique from the left, supporting a path to citizenship for immigrants who are in the country illegally, but speaking out against “an all-out effort” by employers “to bring in cheap labor” through work visas. He is also publicly uncommitted on the measure.

The bill passed 13 to 5 in the Senate Judiciary Committee last week, and supporters are hoping for backing from most Democrats and a sizeable number of Republicans when it comes up for a vote before the full Senate.

Massachusetts Senator Elizabeth Warren has said she supports the bill, and fellow Bay State Democrat William “Mo” Cowan said in a statement that the bill is imperfect but “a huge step forward," which he hopes he can support when it comes up for a final vote.

“We have to ask ourselves, from the left or right, do you want immigration reform or not?” Leahy said in an interview. “I think the time is right to get it.”

Even if the Senate passes the bill, the degree of support and its final form will likely influence negotiations with the House, where lawmakers are more wary of granting illegal immigrants a 13-year path to citizenship, which opponents say amounts to amnesty.

“If we don’t see enforcement, we will see another wave of people entering illegally,” Representative Bob Goodlatte, a Virginia Republican who chairs the House Judiciary Committee, said in an interview.

Goodlatte said his concerns lie primarily with interior enforcement, making sure that people who come to the United States on tourist, student, or work visas are tracked so that they do not overstay their visas. He would also like to see more emphasis on coordinating enforcement with local and state police, and separating out illegal immigrants who should not be granted legal status because of criminal activity or other disqualifying behavior.

Goodlatte has helped lead Republican efforts to consider separate bills dealing with specific immigration concerns, rather than a single proposal deliberated in the Senate.

The Senate bill, by contrast, deals with almost every aspect of immigration law — significantly increasing the number of work visas, requiring employers to use an electronic “E-Verify” database to make sure workers are here legally, and speeding up the process for relatives of legal residents to obtain their own legal residency.

To head off some criticism from House Republicans, the bipartisan group of senators who wrote the bill have made securing the southern border with Mexico the bill’s first condition.

Before any of the nation’s estimated 11 million illegal immigrants can gain legal residency or citizenship, the bill would require the Department of Homeland Security to devise a $3 billion security plan that includes a stronger fence and a strategy to apprehend more of those who cross the border illegally.

No such plan is required for Canada’s border, which has not been a problem for illegal crossings but has been crossed by suspected terrorists.

There are numerous policy reasons to treat the two borders differently, but there are also significant political reasons, analysts say.

“Nobody’s afraid of Canadian immigrants,” said Tamar Jacoby, president and chief executive of ImmigrationWorks USA, a group representing small- and medium-sized businesses in the immigration debate. Members of Congress are not getting calls from voters who are worried about the northern border, she said.

“They’re going to be worried about are we going to be protected from Mexicans?” she said.

Still, groups favoring new immigration laws that include a path to citizenship have not balked at the different standards for the two borders.

“The dynamics are different,” said Eva Millona, executive director of the Massachusetts Immigrant and Refugee Advocacy Coalition, the largest immigration advocacy group in New England. “I don’t think it has to do with prejudice.”

The coalition has been actively lobbying and demonstrating in favor of the bill. The Pew Hispanic Center estimates that more than 345,000 people in the New England states lack legal residency, but the coalition contends that the impact of the bill will be felt by many more people, including legal residents with family members unable to join them. The bill is not perfect, but “we as a country have a great opportunity” for historic change, Millona said.

In addition to inserting language prohibiting a northern border fence, Leahy has also amended the bill to prevent the federal government from collecting a fee for those crossing the border either by foot or car. Leahy and other New England lawmakers have been fighting aggressively on the issue since last month, when the Department of Homeland Security included language in President Obama’s budget proposal to study an admission fee at the borders.

Leahy said maintaining a relatively open border with Canada has been an easy sell among fellow lawmakers, particularly among those from northern states. Canadians in large measure are not looking to settle illegally in the United States for a better way of life, he said, because they already enjoy several benefits, including universal health care.

“They like coming here as tourists, but they want to go back home,” he said.

Canada is Vermont’s largest trading partner, with personal relationships that span generations, Leahy said. His wife was born 200 yards from the border on the American side to Canadian parents who spoke French, and he spent many days of his own youth visiting friends on the other side.

“We’re the envy of the world to have a border like that,” ­Leahy said.

Many who live along the border agree. Roy Amey, co-owner of a log yard and mulch facility in Pittsburg, N.H., 5 miles from the border, said his community would not survive without an easily passable border. He drives his truck across daily, sometimes several times, he said by phone. His daughter-in-law is Canadian, as are many of his employees. Most of his raw bark comes from there as well. At home and at work, he flies two flags.

“If we didn’t have the markets and the business and the trade, they might as well take the northern part of the United States and chop it off,” he said.

BostonGlobe.com complimentary digital access has been provided to you, without a subscription, for free starting today and ending in 14 days. After the free trial period, your free BostonGlobe.com digital access will stop immediately unless you sign up for BostonGlobe.com digital subscription. Current print and digital subscribers are not eligible for the free trial.

Thanks & Welcome to Globe.com

You now have unlimited access for the next two weeks.

BostonGlobe.com complimentary digital access has been provided to you, without a subscription, for free starting today and ending in 14 days. After the free trial period, your free BostonGlobe.com digital access will stop immediately unless you sign up for BostonGlobe.com digital subscription. Current print and digital subscribers are not eligible for the free trial.